Heat exchange for gas, particularly the exhaust gases of an engine

ABSTRACT

A heat exchanger ( 1 ) for gas, in particular the exhaust gases of an engine, comprising a bundle of tubes arranged inside a shell ( 2 ) and intended for the circulation of gas with an exchange of heat with at least one stream of refrigerant fluid, said tubes being fixed by their ends between two support plates ( 5 ) coupled at each end of the shell ( 2 ), and deflection means arranged inside the shell ( 2 ) able to direct the at least one stream of refrigerant fluid inside the shell ( 2 ). The deflection means comprises a longitudinal deflector ( 6, 6   a ) substantially parallel to the tube bundle and intended to divide the shell ( 2 ) into two circuits, said deflector ( 6, 6   a ) being fixed by its longitudinal edges to the internal walls of the shell ( 2 ) and by its transverse edges to the two support plates ( 5 ) by welding. This ensures more effective mounting of said deflector inside the exchanger.

The present invention refers to a gas heat exchanger, in particular forthe exhaust gases of an engine. The invention is particularly applicableto heat exchangers for exhaust gas recirculation in an engine (EGRC).

PRIOR ART OF THE INVENTION

In certain heat exchangers for cooling gases, for example those used insystems recirculating the exhaust gases to the intake of an internalcombustion engine, the two media which exchange heat are separated by apartition.

The present configuration of EGR exchangers on the market corresponds toa metal heat exchanger generally made from stainless steel or aluminum.

There are essentially two types of EGR heat exchangers: the first typeconsists of a shell within which is arranged a bundle of parallel tubesfor passage of the gas, the refrigerant circulating through the shelloutside the tubes, and the second type consists of a series of parallelplates which constitute the heat exchange surfaces such that the exhaustgases and the refrigerant circulate between two plates in alternatinglayers, wherein the exchange of heat may be improved by the addition offins.

In the case of tube bundle heat exchangers, the connection between thetubes and the shell may be of various types. Generally, the tubes arefixed by their ends between two support plates coupled to each end ofthe shell, the two support plates having a plurality of orifices forpositioning the respective tubes.

Said support plates are in turn fixed to means for connection of therecirculation pipe, which may consist of a V connection or a peripheralconnection edge or flange, depending on the design of the recirculationpipe where the exchanger is mounted. The peripheral edge may be mountedwith a gas reservoir, such that the gas reservoir is an intermediatepart between the shell and the edge, or the edge may be mounted directlyon the shell.

In both types of EGR exchanger, the components are largely metallic suchthat they are mounted by mechanical means, then welded in the furnace orby arc or laser welding to ensure the adequate tightness required forthis application. In certain cases, certain plastic components may alsobe included which may have a single function or various functionsintegrated into a single component.

The main function of EGR exchangers is the exchange of heat between theexhaust gases and the refrigerant fluid in order to cool the gases.Furthermore the EGR exchanger must fulfil other secondary functions sothat it can be mounted on the engine block, allow connection with therefrigerant fluid, or allow connection with the exhaust gas circuit,amongst others. At present the various components of the exchanger areattached to the shell by furnace welding or by arc or laser welding.

Certain EGR exchangers with tubes or plates on the market havedeflectors which are placed inside the refrigerant fluid circuit. Thedesign and number of deflectors may vary from one application to thenext, depending on usage requirements and restrictions from the vehiclemanufacturer in terms of operating conditions or restrictions inpresentation of the exchanger.

In most cases, deflectors are used to improve the circulation ofrefrigerant fluid around the gas tubes, thus avoiding stagnation pointswhich could cause boiling of the refrigerant fluid inside the exchanger,and in order to improve refrigeration of all tubes for better efficiencyof the exchanger.

In other cases, deflectors are included to prevent mechanical problemswhich could appear under the working conditions of the exchanger in theengine.

An EGR exchanger is known which uses a longitudinal deflector dividingthe interior of the shell into two halves, in order to direct therefrigerant fluid in bypass mode from one half of the shell to the otherwhen the inlet and outlet pipes for the refrigerant fluid are on thesame side of the shell. This deflector is fixed to the shell of theexchanger by weld points and has a length slightly less than the lengthof the shell.

Spanish patent application number 200931016, not yet published, by thesame holder as the present application, comprises a plurality ofdeflectors arranged transversely along the interior of the shell. Eachdeflector has a surface area smaller than the cross section surface areaof the shell, which allows partial passage of the refrigerant fluid.Said deflectors are not aligned with each other but may be positionedalternately, leaving refrigerant fluid passage zones distributedalternately, thus ensuring correct distribution of the refrigerant fluidas well as improving the mechanical resistance to vibration.

In addition, said deflectors are fixed to the shell by furnace welding.

Patents JP2002292089 and JP2000283666 comprise a plurality of transversedeflectors in the form of plates arranged inside a shell of circularsection. The design of said deflectors is very similar to theconfiguration of the support plates situated at both ends of the shell,the diameter of said deflectors being equal to the internal diameter ofthe shell, and comprise through openings which allow the passage ofrefrigerant fluid. The positions of said passage openings in the variousdeflectors are distributed alternately.

In general, the use of deflectors inside heat exchangers is common andhas become more frequent in recent years, following environmentallegislation and restrictions on the design of certain types ofexchangers, such as:

-   -   heat exchangers which allow the use of two refrigerant fluid        circuits, with the same or different fluids;    -   heat exchangers which must cool two hot fluids, being the same        or different fluids;    -   heat exchangers in which the inlet and outlet pipes for the        refrigerant fluid are on the same side of the shell.

The main problem posed by the use of deflectors is to ensure an adequatetightness between the two circuits defined in the shell of the exchangerwhen two types of refrigerant fluid are used, which is linked to themethod of mounting and fixing the deflector inside the shell, generallyby means of weld points, while ensuring the mechanical strength of theexchanger which must comply with the specifications of the vehiclemanufacturer.

Another problem of this type of deflector is to be able to ensure thecorrect position and orientation of the deflector when it is mounted inthe shell before being welded.

DESCRIPTION OF THE INVENTION

The aim of the gas heat exchanger, in particular for exhaust gases of anengine, in the present invention is to rectify the drawbacks of theexchangers known in the prior art by providing a deflector intended toimprove the distribution of a refrigerant fluid circulating in theexchanger, or to separate two different refrigerant fluids withoutmutual communication inside the same shell, allowing a more effectivemounting of said deflector inside the exchanger.

The heat exchanger for gas, in particular the exhaust gases of anengine, which is the subject of the present invention, is of a typewhich comprises a bundle of tubes arranged inside a shell and intendedfor the circulation of gas with an exchange of heat with at least onestream of refrigerant fluid, said tubes being fixed by their endsbetween two support plates coupled at each end of the shell, anddeflection means arranged inside the shell able to direct the at leastone stream of refrigerant fluid inside the shell, and it ischaracterized in that the deflection means comprises a longitudinaldeflector substantially parallel to the tube bundle and intended todivide the shell into two circuits, said deflector being fixed by itslongitudinal edges to the internal walls of the shell and by itstransverse edges to the two support plates by welding.

This ensures easier positioning and mounting of the deflector inside theshell, and a better fixing thereof thanks to its weld connection. Forpreference, furnace welding is used, thus avoiding the use of weldpoints as in deflectors known in the prior art.

Advantageously, the deflector includes in its longitudinal edges twoperipheral folded fins intended to come into contact with the internalwalls of the shell for its connection by welding.

Also advantageously, the deflector includes in its transverse edges twoprotruding segments able to engage in respective grooves produced in thesupport plates for its connection by welding.

The use of said peripheral fins and protruding segments guaranteesadequate positioning and orientation of the deflector inside the shellbefore it is fixed by welding.

According to a first embodiment, the deflector comprises a closedsurface to prevent communication between the two circuits in the shell.

In this case the exchanger comprises two pairs of inlet pipes and outletpipes provided for the distribution of two different streams ofrefrigerant fluid.

According to a second embodiment, the deflector comprises a throughopening in its surface able to bring the two circuits into communicationin the shell.

In this other case, the exchanger comprises a pair of inlet and outletpipes arranged at the same end of the shell for the distribution of astream of refrigerant fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

For better understanding of the description above, we attach drawingswhich depict diagrammatically, and merely as a non-limitative example, apractical embodiment of the heat exchanger for gas, in particular forthe exhaust gases of an engine, according to the invention, in which:

FIG. 1 is a perspective and partial cross-section view of the heatexchanger of the invention, showing the location of the deflector andthe two circuits through which two refrigerant fluids respectivelycirculate;

FIG. 2 is a perspective view of the deflector according to a firstembodiment of the invention;

FIG. 3 is a perspective view of the deflector according to a secondembodiment of the invention;

FIG. 4 is a perspective view of a type of exchanger which uses a sametype of refrigerant fluid, with its inlet and outlet pipes situated atthe same end of the shell;

FIG. 5 is a cross-section view of the exchanger in FIG. 4, showing thedeflector used and the path of refrigerant fluid;

FIG. 6 is a perspective view of a deflector, showing the longitudinalfixing fins;

FIG. 7 is a partial, perspective view of the shell of the exchanger,showing the deflector mounted and fixed to the internal walls of theshell via the longitudinal fins;

FIGS. 8 and 9 are perspective and plan views respectively of an end ofthe deflector according to the invention, showing a protruding segmentprovided for engagement with a support plate of the tubes;

FIG. 10 is a perspective view of a support plate, showing an engagementgroove intended to receive the protruding segment of the deflector;

FIG. 11 is a perspective view of the deflector mounted in the supportplate illustrated in FIG. 10;

FIGS. 12 and 13 are respectively perspective views of two configurationsof heat exchangers which use two different types of refrigerant fluid,showing the position of the respective pairs of inlet and outlet pipesof the two refrigerant fluids; and

FIG. 14 is a cross-section view in perspective of a heat exchanger usinga single refrigerant fluid, showing the location of the pair of inletand outlet pipes situated at the same end of the shell.

DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1 shows partially a heat exchanger 1 which comprises a bundle oftubes (not shown for reasons of clarity) arranged inside a shell 2,defining an inlet and an outlet 4 for the gas, said tubes being intendedfor the circulation of gases with an exchange of heat with at least onerefrigerant fluid. The tubes are fixed by their ends between two supportplates 5 coupled at each end of the shell 2, the two support plates 5having a plurality of orifices for positioning of the respective tubes.

Thus the exchanger 1 comprises deflection means arranged inside theshell 2 and able to direct the at least one refrigerant fluid in theshell 2. In this case, the deflection means comprises a longitudinaldeflector 6 substantially parallel to the tube bundle and intended todivide the shell 2 into two circuits.

The deflector situated in the shell 2 of the exchanger 1 allows animprovement in distribution of a refrigerant fluid, or the separation oftwo different fluids, such as oil and a refrigerant fluid, withoutmutual communication inside the common shell 2. Two embodiments of thedeflector are shown below.

According to a first embodiment shown in FIG. 2, the deflector 6comprises a closed, homogenous surface which allows a perfect tightnessbetween the circuits of the two refrigerant fluids. The purpose of saiddeflector 6 is to separate two different refrigerant fluids inside theshell 2 because of their different compositions, properties etc. Thistype of deflector 6 is used in exchangers in which it is necessary touse different refrigerant fluid circuits in the exchanger, in order toachieve the exchange of heat with the exhaust gases which circulate inthe tubes.

FIG. 1 illustrates an exchanger 1 which uses said deflector 6 toseparate two types of refrigerant fluid. In this case, two differentinlet pipes 7, 7 a and two different outlet pipes 8, 8 a are necessaryin the same exchanger 1. This ensures adequate separation of therefrigerant fluids in the same shell 2. FIG. 1 depicts the inlet and theoutlet of the two refrigerant fluids in the shell 2, and the inlet andoutlet of the gases in the shell 2 and their change of direction in agas reservoir (not shown).

According to a second embodiment shown in FIG. 3, the deflector 6 acomprises a through opening 9 in the surface for passage of arefrigerant fluid from one half to the other half of the shell 2, inorder to optimize the distribution of the refrigerant fluid in the shell6. This type of deflector 6 a is therefore used to increase theefficiency or improve the distribution of the refrigerant fluid in theshell 2.

FIGS. 4 and 5 illustrate an exchanger 1 which uses said deflector 6 a,the inlet pipe 7 and outlet pipe 8 of which are situated at the same endof the shell 2. On FIG. 4, the inlet and outlet of the refrigerant fluidin the shell 2 are indicated by arrows.

Because of restrictions in presentation or requirements from the vehiclemanufacturer, it is possible that the inlet pipe 7 and outlet pipe 8 ofthe refrigerant fluid must be placed at a short distance from each otheror even at the same end of the shell 2, which may create a preferentialpath for the refrigerant fluid and consequently affect the filling ofthe refrigerant fluid and lead to poor refrigeration of the gas tubes,and also give rise to stagnation points which may cause a phenomenon ofboiling, risking damage to the exchanger. In this case, the deflector 6a with its opening 9 allows an improvement in the circulation of therefrigerant fluid in the exchanger.

The configuration of the deflector 6, 6 a of the present inventionincludes folded peripheral fins 10 in its two longitudinal edges, as canbe seen on FIG. 6, intended to connect the deflector 6, 6 a to twointernal partitions of the shell 2, preferably by furnace welding (seeFIG. 7). In this way, the use of weld points between the deflector 6, 6a and the shell 2, as used with known deflectors of the prior art, iseliminated.

Thus the deflector 6, 6 a of the present invention includes in itstransverse edges two protruding segments 11, as illustrated by FIGS. 6,8 and 9, able to engage in respective grooves 12 produced in the supportplates 5 (see FIGS. 10 and 11), allowing the deflector 6, 6 a to remainfixed in the appropriate position before it is welded. In this case, thedeflector 6, 6 a is mounted in a similar fashion to the mounting processof the tubes with said support plates 5.

For example, FIGS. 1, 12 and 13 illustrate respectively differentconfigurations of exchangers 1 which use two refrigerant fluids, theirrespective inlet pipes 4, 4 a and outlet pipes 8, 8 a being arranged atdifferent positions relative to the shell 2. In this case, a closeddeflector 6 is used (see FIG. 2) to separate the two refrigerant fluids.

Secondly, FIGS. 4 and 14 show respectively different configurations ofexchangers using a same refrigerant fluid, for which the pair of inlet 7and outlet pipes 8 is situated at the same end of the shell 2, saidpipes 7, 8 being arranged at different relative positions in the shell2. In this case, a deflector 6 a fitted with a through opening 9 (seeFIG. 3) is used to improve the distribution of refrigerant fluid.

The deflector 6, 6 a of the invention may be used in exchangers made ofstainless steel or aluminum.

1. A heat exchanger for the exhaust gases of an engine, comprising: abundle of tubes arranged inside a shell for the circulation of gas withan exchange of heat with at least one stream of refrigerant fluid, saidtubes being fixed by their ends between two support plates coupled ateach end of the shell; and deflection means arranged inside the shellable to direct the at least one stream of refrigerant fluid inside theshell, wherein the deflection means comprises a longitudinal deflectorsubstantially parallel to the tube bundle and intended to divide theshell into two circuits, said deflector being fixed by its longitudinaledges to the internal walls of the shell and by its transverse edges tothe two support plates by welding.
 2. The exchanger as claimed in claim1, wherein the deflector includes in its longitudinal edges two foldedperipheral fins configured to contact the internal walls of the shellfor the connection by welding.
 3. The exchanger as claimed in claim 1,wherein the deflector includes in its transverse edges two protrudingsegments able to engage in respective grooves produced in the supportplates for its connection by welding.
 4. The exchanger as claimed inclaim 1, wherein the deflector comprises a closed surface to preventcommunication between the two circuits in the shell.
 5. The exchanger asclaimed in claim 4, which includes two pairs of inlet pipes and outletpipes provided for distribution of two different streams of refrigerantfluid.
 6. The exchanger as claimed in claim 1, wherein the deflectorcomprises a through opening in its surface able to bring the twocircuits into communication in the shell.
 7. The exchanger as claimed inclaim 6, comprising a pair of inlet and outlet pipes arranged at a sameend of the shell for distribution of a stream of refrigerant fluid.